Phyllosilicate and Hydrated Sulfate Deposits: Recorders of Water-Rock Interactions throughout Sinus Meridiani, Mars

High resolution (up to 18 m/pixel) Mars Reconnaissance Orbiter CRISM images (0.4 to 4.0 microns) reveal that exposures of aqueous minerals, including hydrated sulfates and phyllosilicates, occur throughout the Meridiani region. Previous studies have documented expanses of outcrop, or ‘etched terrain' (ET), in Meridiani which have been interpreted to be sedimentary in origin. These deposits overlie Noachian dissected cratered terrain. Mapping at a regional scale using Mars Express OMEGA (0.4 to 5.0 microns) data shows enhanced hydration in several areas of the ET. Kieserite and polyhydrated sulfates were detected in northern Meridiani ET using OMEGA spectral data. CRISM images reveal that hydrated sulfates are more widespread and occur in several spatially isolated exposures throughout the ET. These deposits may represent the remnants of more extensive units that have been partially removed by aeolian erosion. Phyllosilicates have been previously detected using OMEGA data in a crater within northern Meridiani and in a portion of eastern ET. Current mapping with higher resolution CRISM images shows that additional phyllosilicate-bearing deposits occur in several places within the Noachian dissected cratered terrain in the Meridiani region. Fe/Mg smectite dominates the spectral signature of these deposits. Phyllosilicate-bearing deposits within Miyamoto crater occur 120 km to the southwest of the MER rover Opportunity landing site and are located 40 km from the edge of the hematite-bearing plains unit (Hp) explored by the rover. Measurements made by Opportunity show that the outcrop underlying Hp contains the hydroxylated sulfate mineral jarosite, which records acidic formation conditions. The Fe/Mg smectite exposures likely record aqueous geochemical conditions different from those experienced by the outcrop explored by the rover. Continued mapping of alteration minerals using CRISM and OMEGA spectral data combined with geomorphic information will help us to better understand the evolution of the aqueous geochemistry over time in the Meridiani region.